Flotation cell (also called flotation machine) is the main character in flotation process, who is applicable for the separation of nonferrous metal and ferrous metal and nonmetal, such as fluorite and talc.
What is the flotation cell?
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Flotation cell is a kind of flotation separation equipment and one of the common chemical dressing equipment, which mainly separates the mineral by relying on the buoyancy of flotation froth through fitting in with the flotation reagents.
In the whole flotation process, the flotation reagents and pulp are sent to the flotation cell after the mixing. Through the mixing and air inflation of flotation cell, and then complete the flotation froth contacts with and sticks the ore grain to achieve the final mineralization, the objective mineral floats the surface of the pulp with the froth then become a froth layer. And the flotation concentrate is formed, which is discharge from the flotation cell by the scraper or self-flow, unobjective minerals remain in the pulp zone and discharge from the tank.
Basic flotation process of flotation cell
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Flotation cell is the mechanical equipment to complete the flotation process. The flotation operation of general flotation cell includes three parts: pre-flotation operation, flotation operation and post-flotation operation.
1. Pre-flotation: mainly grinding operations -- Crushing the ore and then grinding it fine so that the swimming minerals can be dissociated from other minerals or gangue minerals;
2. Flotation operation: The dissociated minerals are sent to the flotation cell to be added by mixing slurry to make the slurry concentration suitable for the flotation requirements, and the required flotation agents are added to improve the efficiency; Then the pulp in the flotation cell through the air flotation, complete mineral separation.
3. Post-flotation: Dewatering and separating the foam product and tailings product after flotation.
Full flotation process:
1. The pulp is composed of solid mineral particles and water. Using the appropriate flotation agents in the agitation tank for pulp concentration allocation, so as to achieve the flotation requirements.
2. The main purpose of using flotation agents is to increase the hydrophobicity of the mineral surface to float, or to make the minerals not to be floated more hydrophilic.
3. Put the pulp into the flotation cell, the pulp and the air is inhaled into the flotation tank at the same time, the rotating impeller air is pulp turbulent motion break into many froths (adding frother can promote the formation of froths smile and dispersed), air froths in the pulp and the ore grain collision or contact, and according to the surface hydrophobicity of difference to determine whether particles adhesion in froths on the surface, the surface hydrophobicity of ore grain adhesion to the surface of the froths, carried raw float to the pulp page form froth layer, and then be hung as concentrate. And the surface hydrophilic strong particles and froth sattached, still remain in the slurry, be discharged into tailings outside the tank.
What is the working principle of flotation cell?
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1. Working principle of mechanical agitation type flotation cell
When the mechanical agitation type flotation cell works, the slurry and flotation reagents will be delivered to the bottom of the first chamber after fully mixing. The impeller of flotation cell rotates and forms the negative pressure in the cavities, which makes the slurry on the tank bottom and slurry on the tank respectively bring into mixed zone through the upper and under suction, and make the air enter into the mixed zone along the sleeve, so the pulp mixes with air here. Under the centrifugal force of impeller, the mixed slurry is sent to the mineralization zone, and the air forms the bubble then is shattered, and contact with the ore grain to forma the mineralized froth. Under the action of the stator and the turbulent flow plate,the mineralized froth evenly distributes in the cross section of tank, moves up into the separation zone and forms the froth layer, which will be discharged by froth scraper and becomes the froth concentrate.
The unmineralized coal particles above the bottom of the tank will be mixed, mineralized and separated again through the circulation hole and the upper suction port. Part of the pulp under the tank that is not inhaled by the impeller of the flotation cell enters the tank under the second chamber through the middle ore box buried in the pulp. After completing the whole process of the first chamber, it enters the third chamber.Each tank flotation cell repeats the operation until the mine enters the last chamber after the flotation and enters the tailings box to discharge the final tailings.
2. Working principle of air-inflation mechanical agitation flotation machine
When air-inflation mechanical agitation flotation machine works, the motor driving device and the hollow spindle drive the impeller to rotate. The pulp in the slot is sucked in the middle of lower blade of impeller through the inner edge of lower blade of impeller. At the same time, the low pressure air brought from the outside enters the air distributor in the chamber of the lower impeller through the cross rail, air control valve and hollow spindle, and then enters into the middle of lower blade, the pulp fully mixes with the air in the lower blade of impeller, then they are discharged from the outer edge of lower impeller blade.
Due to the combined action of the impeller,cover plate and central cylinder of flotation cell, a certain amount of negative pressure is generated in the impeller blade, so that the medium ore froth and feeding ore flow into the central cylinder through the medium ore pipe and feeding ore pipe, and then enter into the upper impeller blade, and finally discharged from the outer edge of the lower impeller blade. The pulp discharged from the outer edge of impeller under the blade tip and air mixture and impeller blade tip discharge of middlings and feed after installed around the impeller of the stator current and orientation, into the groove of the main body in the pulp, mineralized bubbles rise to the surface of the pulp forming foam layer, pulp part of return under the impeller blade between recycle, the other part through the slot on the partition into the next slot in the circulation of hole seeding or as a final product.
3. Working principle of flotation column
When the flotation column works, add the flotation reagents into the pulp for agitating, then sending them into the flotation column through center feeding equipment. because of the gravity, the pulp slows down from the flotation column, the compressed air diffuses into a large number of tiny air froths after inflation equipment, and evenly distributes on the cross section of flotation column and rises. The pulp and froth acts as convection movement. In this case, part of flotation minerals can attach to the froths, float above the pulp level and form mineralized froths, then the concentrate is overflowed from the froth flow slot or scraped by the scraper. Another part of the gangue cannot be attached to the froth, which is discharged from the tailings lifting device or sent to the next operation.
4. Working principle of impeller flotation machine for ore
When the impeller flotation machine works,the pulp is sent to the impeller from the pulp pipe, then thrown into the slot under the centrifugal force generated by the rotating impeller, then the negative pressure is formed under the cover. The suction air mixed with the pulp together in the upper part of the impeller and then be thrown into the slot, producing negative pressure again. In the slurry, the floating minerals are brought to the surface by the froths to form a mineralized froth layer, and scraped out by a scraper to get concentrate. Other minerals and gangue enters into the middle chamber through the gate on the side wall of the channel and be fed into the next flotation slot. The pulp level in each or several slots can be completed by adjusting the upper and lower gates, and the pulp finish the circulation process in the flotation cell.
5. Working principle of bar flotation cell
The inclined rod wheel that installed on the lower part of the hollow shaft rotates and produces the negative pressure on the flotation wheel. The air is sucked through the hollow main shaft and then separated by the flotation wheel, then the air disperse as tiny froths.
Due to the strong agitating and mass ejection function of the flotation wheel, the pulp mix with the air fully. This mixture pushes ahead first under the effect of inclined rod wheel of flotation wheel, then distributes continuously and evenly by the guide effect of gland and arc plate current stabilizer, and rises towards pulp surface from agitating zone to separating zone under the reflex action of slot bottom, slot wall and the steady flow role of arc plate. The flow path of the mixture is in a"W" shape if seen from the longitudinal section of the slot. Its flow characteristic extends the range of mixing zone relatively and reduces the range of subdivision relatively. In addition, the shallow slot makes the range narrower. The former increases the contact chances between the ore particles and froths, which is beneficial to the mineralization of the froth. The mineralized froth rises to the froth zone and is scraped out by a scraper as the froth product.
The working principle of suction slot is the same as the principle of vertical sand pump. The rotary lifting wheel produces the pressure head, and the pulp is sucked from the guide pipe on slot bottom and lifted to the required height.
Basic requirements when using flotation cell
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As a main equipment for completing the flotation process, here are five requirements during the flotation process according to the flotation practice, froth mineralization theory and hydromechanics research on flotation cell.
1. Good agitating effect
Flotation cell must be able to pressure full amount of air into the pulp and produce a large number of moderate size froths,then the bubbles should also be evenly dispersed throughout the flotation cell.The better the agitating performance is, the better the air dispersion is, and the more even the air froths distribute, so the ore particles can contact the air froths fully, and the process performance of flotation cell is better.
2. Agitating effect
In order to make the ore particles suspend in the slurry, it is required that the flotation cell should have a proper and uniform agitating effect, so that the ore particles and reagents can disperse fully in the slot. In addition, agitating can promote the contact and adhesion between ore particles and metal froths, which contributes to the dissolution and dispersion of refractory reagents.
3. A certain thickness of stable froth layer
The mineralized froth layer can not only retain the target mineral, but also make part of the mixed gangues fall off from the froth, which is beneficial to the "secondary enrichment". Besides,adjusting the pulp level can control the flow rate of pulp and the thickness of the froth layer.
4. Continuous working, easy to adjust
Generally, the industrial flotation cell should be equipped with continuous ore feeding, scraping and discharging mechanism, which can ensure the continuous working of flotation cell. In addition, the flotation cell should also be equipped with the mechanism that adjusts the pulp level, thickness of froth layer and pulp flow speed.
5. Program simulation and remote control capability
In the design of modern flotation cell, the automation of mineral processing plant requires not only reliable flotation cell, durable parts, but also the program simulation and remote control capability.
Selection principle of flotation cell
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The selection of flotation cell is an important factor that relates to the flotation efficiency of the flotation cell.Here are few selection principles of the flotation cell:
1. Select the flotation cell according to the ore properties
The ore properties mainly include ore selectivity, ore particle size, ore density, ore grade and pH value, etc. if the ore is easy to separate and the required amount of air inflation is little,mechanical agitation type flotation cell is a good choice, on the contrary, air-inflation mechanical agitation flotation machine is better. KYF flotation cell, BS-K type flotation cell and CLF type coarse particle flotation cell can be selected when the ore particle size is coarse. And the flotation column can be used when the ore is featured with fine selected grain size, high grade, low pH value, easy to be separated.
2. Select the flotation cell according to the size of mineral processing plant
In general, large size flotation cell is used in the large mineral processing plant, medium and small size of the flotation cells are applied in the medium and small size of mineral processing plant.
3. Select the flotation cell according to the separating degree
Generally, flotation can be divided into cleaning,roughing and scavenging, of which, the purpose of cleaning is to improve the concentrate grade, so the froth layer should be thinner, which can make the gangue separated easily. Better not to choose the flotation cell with a large charging.
Classification of flotation cell
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Flotation cell was first originated in China's Ming dynasty, which was used in medicine and metallurgy industry. Relying on the natural hydrophobicity of mineral surface to purify the mineral drugs, the fine mineral powder would float on the surface, and separate from the sinking gangue. At the end of the 19th century, in order to improve the mineral separation, the flotation process was clearly proposed due to the increasing demand for metallic minerals.
Today, there are many kinds of flotation cells, which can be divided into different types according to the inflating method, agitating method, structure of the stator and rotor, the shape and depth of the slot, the movement mode of pulp in the slot, the circulation mode and the entering way of flotation cell slot, and the discharging way of froth product. According to the classification of the flotation cell, the flotation cell can be divided into four types:
1. Mechanical agitation type flotation cell
The main feature of mechanical agitation type flotation cell is that the inflation and agitation of pulp are realized by the mechanical agitator with self-slurry suction and self-air suction. In the flotation process, the middle product of mechanical agitation type flotation cell can return without pump lifting. Therefore, this kind of flotation cell has advantages in the process configuration. In addition, it can achieve self-slurry suction, so it does not need the external fan.
According to the different models, mechanical agitation type flotation cell can be divided into: XJK flotation cell (also named as A flotation cell), SF flotation cell, JJF flotation cell and XJB flotation cell.
2. Air-inflation mechanical agitation flotation cell
The main difference between air-inflation mechanical agitation flotation machine and mechanical agitation type flotation cell is that the air-inflation mechanical agitation flotation machine belongs to external air supply, whose agitator only plays the role of agitating, and the air is forced into the air by the external fan.
As the air is supplied by an external fan,the inflating volume of the air-inflation mechanical agitation flotation machine can be adjusted by the valve according to the requirements of flotation production.The impeller, which only acts as an agitating impeller, has a low rotating speed and weak agitating effect, so it is not easy to produce slime phenomenon for floating the brittle minerals; and the slurry surface is relatively stable,and easy to form a stable foam layer, which is conducive to improving the separating index. Because the rotating speed of impeller is low and the pulp flows by the gravity, the power consumption per unit is low, the service life is long, and the maintenance cost is low.
Because the air-inflation mechanical agitation flotation machine cannot achieve self-slurry suction,the return of middle products needs pump lifting. And the air supply equipment needs to be equipped, which is not easy to manage. Therefore, air-inflation mechanical agitation flotation machine is often used to deal with the simple roughing and scavenging operation.
According to the different models, the air-inflation mechanical agitation flotation machine can be divided into: KYF flotation cell, XCF flotation cell, BS-K flotation cell, CLF flotation cell.
3. Flotation column
Flotation column is a kind of air-inflation flotation cell. There is no mechanical agitator and transmission part in flotation column, so the pulp inflation is achieved by the external air compressor.
The features of flotation column are simple process flow and structure, low power consumption, less wear parts and easy to operate and manage. However, the aerator of flotation column is easy to be blocked due to calcium formation in the alkaline pulp. Therefore, the flotation column is more suitable for the roughing and scavenging of those free-milling ores with simple composition and high grade.
4. Gas evolution type flotation cell
Gas evolution type flotation cell is also known as variable pressure flotation cell or step-down flotation cell. The biggest feature of gas evolution type flotation cell is that it can precipitate a large number of froths from the solution. At present, gas evolution type flotation ell can be divided into jet flotation cell, cyclone flotation cell.
In China, the research and development of flotation cell started late, starting in the mid-1950s. the first three kinds of flotation cells are very widely used in mineral processing plants among the above four types of flotation cell.